Back support for a chair

ABSTRACT

An office-type chair including a back support having a suspension mesh back support and a back support frame. The suspension mesh back support has an integral retaining channel disposed at a peripheral edge thereof, and the back support frame includes a central pair of upright support posts and wedge base for mounting to a chair frame. The back support frame includes a plurality of flexible and spaced support arms extending laterally outward from the upright support posts. The support arms each have a peripheral edge configured for fastenerless attachment in a tensioned state within the suspension mesh retaining channel. An upholstery cover encapsulates the suspension mesh and back support frame. The office chair also includes a lumbar mechanism including a resilient cushion that may be positioned in the space between the suspension mesh and the support frame and adjusted along the vertical extent of the back support by rolling the resilient cushion on the rear of the suspension mesh.

BACKGROUND OF THE INVENTION

The present invention relates to an office chair and more particularly,to an office chair that provides a flexible backrest portion of anoffice chair.

The market for office seating continues to demand more than just a placeto sit. Today's users want comfort, function, and adjustability, all inan aesthetically pleasing configuration. More recently, it is known foroffice chairs to have a back support structure that includes a flexiblematerial, such as a woven mesh fabric, attached in tension to aperipheral frame. These arrangements can provide a high degree ofcomfort, even over extended periods of time. They are, however,typically limited by the relative rigidity of the peripheral frames, andthe relative cushioning of the woven mesh fabric. The frame mustgenerally be rigid in order to support the mesh fabric in tension, andthe rigidity places limits on the flexibility of the back support. Insome instances, a rigid peripheral frame may be uncomfortable for anoccupant and prevent flexibility as the occupant attempts to adjusttheir posture while seated. As such, manufacturers and users alike mayseek a degree of torsional flexibility in the back support for addedcomfort and increased range of movement while seated in the officechair, while retaining the long term comfort and cushioning that thetensioned fabric provides.

SUMMARY OF THE INVENTION

The present invention provides a back support that includes a supportframe and a suspension mesh material that are specifically designed towork with one another to provide desired support characteristics andtorsional flexibility for an occupant while sitting in the associatedchair. The frame may have a flexible portion that supports thesuspension mesh material in tension. The mesh material may be molded andflexible. These components can be individually tuned to provide the backsupport with desired support characteristics, including variations inshape and support at different locations on the back support. In oneembodiment, an upholstery cover may overlie at least a portion of thesuspension mesh. The characteristics of the cover are such that it doesnot impede the flexible relationship of the frame and the suspensionmesh.

In one embodiment, the flexible portion of the back support frame isformed by a plurality of flexible and spaced support arms that extendoutwardly from one or more upright support posts. The support arms mayeach have peripheral edges that form the periphery of the frame. Thesupport arms are spaced apart from one another such that each of thesupport arms can be independently flexed at the periphery. The one ormore upright support posts may include a pair of spaced apart supportposts that generally define a central opening therebetween, wherein thesupport arms may extend outwardly from one of the upright posts. In suchan embodiment with two spaced apart support posts, the posts may eachform an axis about which each support post can twist—independent of oneanother—in response to movements by a user that place a load on thesupport arms extending from one or the other of the support posts.

The suspension mesh may be supported in tension by the flexible portionof the back support frame—without the need for a rigid peripheral frame.In one embodiment, the suspension mesh has an integral retaining channeldisposed at a periphery thereof, which is configured for fastenerlessattachment to the peripheral edges of the support arms in order to holdthe suspension mesh in a tensioned state with respect to the supportframe. The support arms may be flexed from a first “pre-tensioned”position into a second tensioned position when the suspension mesh ismounted to the support arms. In this tensioned position, the supportarms may allow the back support to promote a desired ergonomic contour,and further provide the back support with desired supportcharacteristics. The tensioning of the supports arms prior to the usersitting in the chair creates a predetermined reactionary force thatbiases the suspension mesh towards the ergonomic contour when a userplaces a load on the back support. More particularly, the tensioning ofthe support arms provides a reactionary force that increasesexponentially with an increase in load from a user, such that the backsupport accommodates a wide variety of users and user types.

In another embodiment, the suspension mesh is a molded material thatincludes spaced horizontal tensioning support members and spacedvertical tensioning support members that together form a flexible meshthat distributes the load placed on the back support by the user. Thesupport characteristics provided by the suspension mesh may be tuned asdesired by varying one or more of a number of features of the meshincluding the width, thickness, spacing and a pattern of the horizontaland vertical support members.

The fabric cover may be an upholstery cover formed from a knittingprocess. The knitting process may be a three dimensional, loftedknitting process that gives the cover a degree of elasticity, such thatthe cover does not impede the support frame and suspension mesh fromproviding a desired support profile. In one embodiment, the fabric covermay encapsulate at least a portion of the suspension mesh and backsupport frame. In another embodiment, the fabric cover may extend overthe surface of the suspension mesh facing the user. The cover may alsowrap around the periphery of the suspension mesh and at least a portionof the rear surface of the support frame. In a more particularembodiment, the cover may wrap around the rear surface of the supportframe leaving the central opening between the support posts exposed,with a portion of the cover extending into a spline channel in the frameadjacent the support posts to attach the cover to the back support in afastenerless manner. For example, an extrusion may be disposed withinthe upholstery cover edging. The edging, including the extrusion, isinserted into the spline channel of the support frame such that theupholstery cover can be mounted to the back support without additionalfasteners or adhesive.

In another embodiment, the support characteristics of the back supportmay be tuned to a desired profile by varying the features of the backsupport frame, such as the number, length, thickness, and the initialposition of the support arms. For example, longer or narrower supportarms, or more spaced apart support arms, may provide a greater degree offlexibility. In addition, in an embodiment where the suspension mesh issupported in tension between the peripheral edges of the support arms,the initial position of the support arms (i.e., prior to the attachmentof the suspension mesh) may be set to a predetermined degree thatrequires an amount of flexing of the support arms in order to attach andretain the suspension mesh, wherein the support arms have a desireddegree of flexed tension when supporting the mesh. A greater degree ofmovement from the pre-tensioned to the tensioned positions of thesupport arms increases tension in the support arms, making them feeltighter and more supportive to a user and altering the reactionary forcenoted above. The flexed state of the support arms may further help toretain the suspension mesh on the support frame.

In another embodiment, the back support defines thoracic, shoulder,lumbar, and pelvic regions, and the support characteristics provided bythe combined back support frame and suspension mesh may be different inthe different regions. For example, the support characteristics of thesupport arms of the back support frame and the width, thickness andspacing of the horizontal and vertical support members of the suspensionmesh may be varied at different locations of the back support to createareas of increased support and areas of increased compliance dependingon the desired functionality.

In another embodiment, the back support includes a lumbar mechanismpositioned adjacent the rear side of a flexible back support surface,such as the rear side of the suspension mesh. The lumbar mechanismincludes a resilient lumbar pad or cushion that has a portion in contactwith the rear side of the flexible back support in at least the lumbarregion. The resilient lumbar pad is adjustable along the vertical extentof the rear side of the flexible back support surface by rolling theflexible lumbar pad on the rear side of the flexible back supportsurface. In one embodiment, the resilient lumbar pad is a hollow,cylindrical cushion or pillow that can roll along the rear side of theflexible back support surface.

In another embodiment, the lumbar mechanism is positioned on a backsupport that includes a support frame with a pair of spaced apartupright support posts, and a flexible back support surface connected tothe support frame. The lumbar mechanism is positioned between the backframe and the flexible back support surface and includes a lumbar pad,at least a portion of which engages the flexible back support surface.The lumbar pad is visible through the window defined between the supportposts on the back frame. A handle may connect to the lumbar pad andextend through the window for access by the user.

In another embodiment, the lumbar mechanism includes a pair of spacedtracks mounted to upright support posts of a back support frame; and acarriage that is attached to the lumbar pad. The carriage is verticallymoveable along the spaced tracks to adjust the vertical position of atleast a portion of the lumbar pad. Further, the carriage may include ahandle and a pair of opposed lateral portions, and the track may includea series of detents. The lateral portions of the carriage are configuredto mount the carriage to the tracks and to interface with the detentssuch that the vertical position of the lumbar pad can be retained at adesired position.

According to another embodiment, a method of manufacturing andassembling the back support is provided. The method generally includes:(a) molding the back support frame; (b) molding the suspension mesh; and(c) mounting the back support frame to the suspension mesh. In oneembodiment, the method further includes mounting the lumbar mechanismwithin the space between the back support frame and the suspension mesh.

These and other objects, advantages, and features of the invention willbe more fully understood and appreciated by reference to the descriptionof the current embodiments and the drawings.

Before the embodiments of the invention are explained in detail, it isto be understood that the invention is not limited to the details ofoperation or to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention may be implemented in various other embodimentsand may be practiced or may be carried out in alternative ways notexpressly disclosed herein. Also, it is to be understood that thephraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting. The use of“including” and “comprising” and variations thereof is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items and equivalents thereof. Further, enumeration may beused in the description of various embodiments. Unless otherwiseexpressly stated, the use of enumeration should not be construed aslimiting the invention to any specific order or number of components.Nor should the use of enumeration be construed as excluding from thescope of the invention any additional steps or components that might becombined with or into the enumerated steps or components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an office chair having a back supportaccording to one embodiment of the present invention;

FIG. 2 is a front perspective view of the back support, with anupholstery cover removed;

FIG. 3 is a rear perspective view of the back support, with theupholstery cover removed;

FIG. 4 is a rear view of a back support frame of the back support ofFIG. 1;

FIG. 5 is a front view of the back support frame;

FIG. 6 is a side view of the back support frame;

FIG. 7 is a front view of a suspension mesh back support of the backsupport of FIG. 1;

FIG. 8 is a rear view of the suspension mesh back support;

FIG. 9 is a detail view of a rear portion of the back support frame,taken from FIG. 4 and illustrating a spline channel;

FIG. 10 is a detail view of a rear portion of the suspension mesh backsupport, taken from FIG. 7 and illustrating a retaining channel;

FIG. 11 is a rear view of the upholstery cover;

FIG. 12 is a front view of the upholstery cover;

FIG. 13 is a detail and cross-sectional view of the back support framemounted to the suspension mesh back support, illustrating a first curvedposition A and a second curved position B;

FIG. 14 is a front perspective view of the back support frame,illustrating the first curved position A;

FIG. 15 is a front perspective view of the back support frame,illustrating the second curved position B;

FIG. 16 is a flow chart depicting a method of manufacturing the backsupport;

FIG. 17 is and exploded view of the back support, including a lumbarsupport unit, according to another embodiment of the present invention;

FIG. 18 is cross-sectional view of the back support, taken along lineXVIII-XVIII of FIG. 28;

FIG. 19 is a front detail view of a carriage and tracks of the lumbarsupport unit of FIG. 17;

FIG. 20 is a front perspective detail view of the carriage and tracks;

FIG. 21 is a front perspective detail view of a portion of the carriageand a track;

FIG. 22 is a cross-sectional view of the carriage and a track, takenalong line XXII-XXII of FIG. 20;

FIG. 23 is a front perspective detail view of the carriage and tracks,illustrating distorted track alignment;

FIG. 24 is a front perspective detail view of a portion of the carriageand a track, illustrating distorted track alignment in one direction;

FIG. 25 is a front perspective detail view of a portion of the carriageand a track, illustrating distorted track alignment in the oppositedirection;

FIG. 26 is a cross-sectional view through a shoulder screw that mountsthe track to an upright support post of the back support, illustratingflexibility of the attachment with the track angled in one direction;

FIG. 27 is a cross-sectional view through a shoulder screw, track, andupright support post, illustrating flexibility of the attachment withthe track angled in another direction;

FIG. 28 is a rear view of the back support, illustrating the lumbarsupport in a lowered position;

FIG. 29 is a rear view of the back support, illustrating the lumbarsupport in a mid or home position;

FIG. 30 is a rear view of the back support, illustrating the lumbarsupport in a raised position;

FIG. 31 is a perspective, cross-sectional view of the back support,taken along line XXXI-XXXI of FIG. 28 and illustrating the lumbarsupport in a lowered position;

FIG. 32 is a perspective, cross-sectional view of the back support,taken along line XXXI-XXXI of FIG. 28 and illustrating the lumbarsupport in a mid or home position;

FIG. 33 is a perspective, cross-sectional view of the back support,taken along line XXXI-XXXI of FIG. 28 and illustrating the lumbarsupport in a raised position;

FIG. 34 is a cross-sectional view of the back support, taken along lineXXXI-XXXI of FIG. 28 and illustrating the lumbar support in a loweredposition;

FIG. 35 is a cross-sectional view of the back support, taken along lineXXXI-XXXI of FIG. 28 and illustrating the lumbar support in a mid orhome position; and

FIG. 36 is a cross-sectional view of the back support, taken along lineXXXI-XXXI of FIG. 28 and illustrating the lumbar support in a raisedposition.

DETAILED DESCRIPTION OF THE CURRENT EMBODIMENT

I. Overview

An office-type chair 10 is shown in FIG. 1 and generally includes a backsupport 12 constructed in accordance with an embodiment of the presentinvention. Although FIG. 1 illustrates the back support 12 as part of acomplete chair 10 with a seat support 3 and other support structure,this is only exemplary. The back support 12 may be generally used inconnection with any structure intended to provide seated back support.In particular, the embodiments of the office chair 10 disclosed in thepresent application include the back support 12 for comfortablysupporting the back of a user and an efficient method of manufacturingand assembling such a back support.

FIG. 1 shows a view of an exemplary version of the chair 10. The officechair 10 generally includes a chair frame 2, a seat support 3, andoptional armrest assemblies 4 extending from the chair frame 2. The seatsupport 3 defines an upward facing support surface on which the occupantis supported. The chair frame 2 may include a height adjustable base 5having plurality of outwardly extending legs 6 to which casters 7 arepivotally mounted. Further, the chair 10 may include a tilt controlmechanism.

The back support 12 of the present invention defines thoracic X(including shoulder W), lumbar Y, and pelvic regions Z as illustrated inFIG. 1. The support characteristics provided by the back support 12 maybe different in the different regions W-Z. The lumbar and pelvic regionsY, Z provide the greatest support, while the thoracic region X providesthe least support. The shoulder region W (a subset of the thoracicregion X) provides high flexibility and low pressure, specificallyagainst the occupant's shoulders. Likewise, the rest of the thoracicregion X is also configured to provide high compliance and low pressure,while bridging the support characteristics between the shoulder andlumbar regions. The lumbar region Y has a natural support curve, whichaids in comfort and proper posture for a seated occupant. Lastly, thepelvic region Z offers the most support and the least flexibility, andhelps rotate the occupant's pelvis forward in order to assistmaintaining lordosis in the lumbar spine which helps balance the muscleload and reduces loading on the intervertebral ligaments and discs aswell as reducing pressure on the sacrum/coccyx when an occupant issitting.

II. Structure

Referring to FIGS. 2-6, the back support 12 has a contoured shape thatpromotes proper posture the back of an occupant. The back support 12comprises a suspended or suspension mesh back support 14, referred toherein as “suspension mesh,” and a back support frame 16. As shown inFIGS. 4-6, the support frame 16 includes a central pair of generallyupright support posts 18 and a plurality of flexible and spaced supportarms 20 extending laterally outward from the support posts 18. In theillustrated embodiment, the support frame 16 also includes a lower wedgebase 22 for mounting the back support 12 to the chair frame 2. Asillustrated, the upright support posts 18 are joined at an upper end bya support cross member 21 and at the lower end by an upper portion ofthe lower wedge base 22 (which also forms a support cross member), whichcollectively define an internal central opening 23 or “window”therebetween. In one embodiment, the support posts 18 and cross members21, 22 may be provided with a predetermined degree of flexibility. Theback support 12 may have a contoured shape that helps promote properposture for the occupant. In particular, as seen in FIG. 6, the lowerportion of the mesh 14, when suspended by the support frame 16, isgenerally convex and the upper portion curves forwardly and is generallyconcave such that the back support 12 approximates the neutral postureaxis of the occupant's spine.

The support frame 16 may be formed from a variety of materials, such asan injection molded plastic; and the support posts 18 and the supportarms 20 may be formed integrally from a single piece of molded plastic.In one embodiment, the entire support frame 16 is molded as a unitarypiece, with portions of the support frame 16 molded to predetermineddimensions that will provide the overall back support 12 with a desiredsupport profile when the support frame 16 is combined with thesuspension mesh 14 as defined in more detail below. The support posts 18provide support for the back support 12, but may also provide a degreeof torsional flexibility for the back support 12. For example, thesupport posts 18 may have a controlled degree of torsional deflectionand resiliency such that they are capable of twisting about an axis(defined by the longitudinal length of the support post 18) under theforce of an occupant's back on the support arms 20, which enables theback support 12 to move with the occupant as the occupant shifts fromside to side, leans, or twists. More particularly, in an embodimentwhere the frame includes a pair of spaced apart support posts 18 and thesupport arms 20 extend outwardly from each of the support posts 18, aportion of each individual support post 18, between the upper 28 andlower 22 cross members, may have a degree of independent torsionalflexibility such that the portion of each support post may independentlytwist about the axis as a user leans against and flexes one or more ofthe support arms 20 that extend outwardly from that particular supportpost 18. This two-point flexing (each support post 18 twisting about itsown longitudinal axis in an opposite direction from the other supportpost 18) may be advantageous in that it moves the neutral deflectionaxis between the two support posts 18 closer to the occupant's spine,whereas a single support arm and flex point would cause the occupant torotate about the back, rather than with it.

The support arms 20 each have a peripheral edge 24 and may extendgenerally parallel to one another. In the illustrated embodiment, thesupport arms 20 include a width extending in a generally verticaldirection, and the width tapers as the support arms 20 approach theperipheral edge 24. The support arms 20 are spaced from one another andinclude a gap 26 between adjacent arms 20. In the illustrated embodimentwhere the width of the support arms 20 tapers, the spacing betweensupport arms increases approaching the peripheral edges 24. In theillustrated embodiment, the gaps 26 between adjacent arms do not extendentirely to the support posts 18, which may slightly increase thestrength of the support arms 20 near the support posts 18.Alternatively, the gaps 26 may extend completely to the support posts18. In an alternative embodiment, the arms may slightly converge ordiverge as they approach the peripheral edge 24.

Further, the support arms 20 are molded to have a slight first position“A” in an initial state prior to attachment to the suspension mesh 14,as will be described in more detail below. As shown in FIGS. 4-6 and12-13, in the first position A, referred to as the pre-tensioned state,the support arms 20 are angled slightly rearward, toward the rear of theoffice chair 10, such that they can then be flexed to a more forward andtensioned position—as described in more detail below—when connected tothe suspension mesh 14. The support characteristics provided by thesupport frame 16 are based, at least in part, on the length, thickness,number and the pre-tensioned position or curvature of the support arms20. The size of the gap 26 between adjacent arms 20 also influences thesupport characteristics provided by the support frame 16. In anotherembodiment, the back support 12 may be formed without the plurality ofsupport arms, for example, by forming a single, unitary flexible portionthat may be curved as desired in a pre-tensioned state.

Referring additionally to the detail view of FIG. 9, the support frame16 includes a spline channel 28. The spline channel 28 is generally agroove that extends along the length of each of the support posts 18adjacent to each of the support posts on a rear surface of the supportframe 16. The spline channel 28 also extends between the upper ends ofthe support posts 18, along the cross member 21, at an upper end of thesupport frame 16. In the illustrated embodiment, the spline channel 28is a continuous channel, however, in another embodiment the splinechannel may be a series of intermittent channels. As discussed in moredetail below, the spline channel 28 provides an attachment structure forthe cover 60 extending over the support frame 16 and suspension mesh 14.

As illustrated, the wedge base 22 is one option for attaching thesupport frame 16 to the base 5. As seen in FIGS. 4-6, the wedge base 22protrudes from a lower portion of the support frame 16 and is configuredto be received in a rigid portion of the base 5. In this embodiment, thewedge base 22 and base 5 have mutually complementing shapes, and thewedge base 22 is fitted into the base 5 in a generally male/female typeconnection. Although not shown, a fastener may be installed from a lowersurface of the base, through the base 5, and into the wedge base 22,connecting the components primarily in tension. Of course, in analternative embodiment, the back support 12 may connect to the base 5 byanother method.

As noted above, the suspension mesh 14 may be a one-piece, moldedperformance material that is suspended in a degree of tension on thesupport frame 16 to extend in front of the front surface of the supportframe 16. The suspension mesh 14 may be arranged in such a manner that,when supported on the support frame 16 via the tensioned support arms20, it provides desired support characteristics to accommodate a widevariety of user types. In one embodiment, the suspension mesh 14 ismolded or otherwise formed from a flexible material, which may be aflexible polymer such as a thermoplastic elastomer, and, in a moreparticular embodiment, may be a thermoplastic polyurethane or athermoplastic polyester. Referring now to FIGS. 7-8, the suspension meshprovides a load bearing surface that supports the back of the occupant.In the illustrated embodiment, the suspension mesh 14 includes spacedhorizontal tensioning support members 40 and spaced vertical tensioningsupport members 42 that together form a flexible mesh to distribute theload applied by the user. The horizontal support members 40 aregenerally uniformly spaced apart from one another across the verticalextent of the suspension mesh 14, and each horizontal support member 40has approximately the same width extending in a vertical direction. Inone embodiment, the horizontal support members 40 may be thicker in thelumbar region and in the pelvic region to provide a degree of additionalsupport in those regions. The vertical support members 42 are generallyuniformly spaced from one another across the lateral extent of thesuspension mesh 14, and in the illustrated embodiment the verticalsupport members 42 gradually increase in thickness in a lateraldirection from the upper end of the suspension mesh 14 toward the lowerend of the suspension mesh 14, such that the vertical support members 42are thicker within the lumbar and pelvic regions of the suspension mesh14 to provide a degree of additional support in the lumbar region.Further, the suspension mesh 14 may include two shoulder supports 44formed by spaced radial arrays 46 that are disposed at the upper cornersof the suspension mesh 14. The radial arrays 46 are diagonal bands thatare relatively thin and widely spaced, the purpose of which will bediscussed below. The support characteristics provided by the suspensionmesh 14, both as an overall arrangement and in the variations betweendifferent regions, are based, at least in part, on the thickness andspacing of the horizontal and vertical tensioning support members 40, 42and the radial arrays 46. As noted above, the arrangement shown in theillustrated embodiment is tuned to provide desired supportcharacteristics in the desired locations for a wide variety of usertypes; however, the thickness, depth and spacing of the support members40, 42 may be varied from application to application in order to providethe suspension mesh 14 with an alternative support profile. For example,in another embodiment, added support may be provided at other regions,for example, by increasing the thickness of the vertical 40 orhorizontal support members 42 in that region, or by decreasing thespacing between horizontal support members 42 in that region or acombination of these features.

Referring still to FIGS. 7-8, the profile of the suspension mesh 14—whenattached to the support frame 16—has a predetermined contour thatsupports a typical chair occupant in an appropriate posture,ergonomically supporting the back of the occupant. This contour is theresult of the predetermined tuning of the back frame 16 and support arms20 in the pre-tensioned state, such that when the support arms 20 aremoved into a tensioned state with the attachment of the suspension mesh14, each support arm 20 has a desired position and a desired amount oftension for the support arms 20 and mesh 14 to collectively form thedesired contour. More particularly, the front surface of the suspensionmesh 14 has a generally convex shape in the pelvic and lumbar regions toprovide support to those regions of the user's back, whereas the upperportion of the front surface of the suspension mesh 14 (in the thoracicand shoulder regions) is generally concave. When loaded with the weightof an occupant, the back support 12 provides flexibility as noted abovedue to the individual flexibility of the support arms 20 and thecompliance of the mesh 14, while continuing to encourage this ergonomicuser posture.

Referring to the detail view of FIG. 10, the suspension mesh 14 includesan integral retaining channel 48 disposed at a peripheral edge 50 of thesuspension mesh 14. As noted below, the retaining channel receives theperipheral edges of the support arms 20 on the support frame 16 toattach the suspension mesh 14 to the support frame 16. The retainingchannel 48 is configured such that an opening 52 is disposed on a rearsurface of the suspension mesh 14 at a periphery of the suspension mesh14 and the retaining channel 48 is open toward the center of thesuspension mesh 14. The retaining channel 48 is molded to be rigid formounting, yet flexible enough to allow a needed degree of localizedflexing, as described in greater detail below. In the illustratedembodiment, the retaining channel is intersected by a series of spacedapart dividers 47 to provide the channel with a degree of support thatprevents the channel from being pulled open. The dividers may be spacedapart at a distance greater than the width of the peripheral edges ofthe support arms 20, such that the support arms 20 are not overlyconstrained within the receiving channel 48 and each individual supportarm 20 is enabled a degree of twisting and sliding movement within thechannel 48. As noted, the suspension mesh 14 may be formed from avariety of materials; and the horizontal and vertical tensioning supportmembers 40, 42, radial arrays 46, and retaining channel 48 areintegrally formed as a single component.

Referring now to FIGS. 11-12, front and rear views of an upholsterycover 60 are illustrated. In one embodiment, the upholstery cover 60covers at least a portion of the support frame 16 and suspension mesh14, defining a suspension surface 62 against which the back of a seatedoccupant is supported. In one embodiment, the upholstery cover 60 is inthe form of a substantially contoured pocket with an open lower end 64and is sized and shaped to fit snugly about the periphery of thesuspension mesh 14 as the suspension mesh 14 is suspended on the supportframe 16. In the illustrated embodiment, the upholstery cover 60includes a central opening 66 extending upwardly from the opening 64 atthe lower end along the rear surface of the cover 60 and aligned withthe window 23 in the support frame 16. The central opening 66 mayinclude a pocket-type edging 68 formed in the perimeter of the centralopening 66, and an elongated extrusion 70 (not shown) disposed withinthe edging 68. The central opening 66 and edging 68 are configured tosubstantially match the shape of the support frame 16 spline channel28—extending around the window 23 in the support frame 16—for mountingthe upholstery cover 60 to the back support 12, as will be described infull detail below.

The upholstery cover 60 can be made of a three-dimensional, lofted,spacer knit fabric that provides form fitting stretch qualities and aswell as cushioning characteristics. In this embodiment, the lofted knitof the upholstery cover 60 provides a degree of stretch in theupholstery fabric 60 that enables some stretching of the cover as theframe 16 and suspension mesh 14 flex. In one embodiment, the upholsterycover 60 knit construction is somewhat visually translucent, yet isthicker than traditional knits or weaves. The knit fabric constructionallows a level of stretch and recovery without elastomeric content suchthat the cover 60 does not prevent movement and flexing of theunderlying suspension mesh 14 and frame 16. Further, the knittingprocess may enable the upholstery cover 60 to be knit in a patternwithout having to use sewing or other fastening means.

To provide additional support to the occupant, the back support 12optionally includes a lumbar support unit 80 which is configured tosupport the lumbar region of the occupant's back and is adjustable toimprove and customize the comfort of this support. The lumbar supportunit 80 is positioned between the suspension mesh 14 and the supportframe 16. In one embodiment, the lumber support unit 80 is adjustable byrolling a resilient lumbar pad 82 along a portion of the rear surface ofthe suspension mesh 14.

Referring now to FIGS. 17-36, the lumbar support unit 80, also referredto as the lumbar mechanism 80, includes a resilient pillow or lumbar pad82, a pair of spaced tracks 84, and a carriage 86 mounted between thetracks 84. In one embodiment, the lumbar pad 82 is a flexible cushionthat is compressed between the suspension mesh 14 and the back supportframe 16 and capable of conforming when experiencing a load from theoccupant. More particularly, the lumbar pad 82 is a hollow, tubularcushion that is a cylindrical body 88 having opposing open ends 90 whenin an uncompressed state. The pad 82 may be deformed out of thecylindrical shape when positioned between the suspension mesh 14 and thesupport frame 16. In one embodiment, the lumbar pad 82 may be made of asoft, translucent plastic material.

As illustrated, the lumbar pad 82 includes plurality of annular supportribs 92 that are integrally molded in the cylindrical body 88 and areconfigured to provide a desired degree support to the lumbar mechanism80. The support ribs 92 extend around the circumference of the body 88and are spaced from one another. More or fewer support ribs 92 may bemolded into the body 88 than are shown in the illustrations, and thespacing between the support ribs 92 may also be adjusted to modify thesupport characteristics of the lumbar pad 82. In the illustratedembodiment, the number and spacing of the support ribs is predeterminedto provide the pad 82 with a desired deflected profile when the pad 82is deformed between the suspension mesh 14 and the frame 16 and furtherdeformed when experiencing a load from a user. The illustrated pad 82includes two groups of support ribs 92. A first group 93 of threesupport ribs 92 is positioned adjacent one end of the pad 82, with afirst one of the ribs 92 in the group 93 spaced from the end of the pad,and two additional ribs 92 in the group 93 positioned inward from thefirst rib such that each rib 92 in the group 93 is spaced from anadjacent rib 92 in the group 93 at the same distance. The group of ribs95 is disposed at the opposite end of the pad 82 with similar spacing.The groups 93 and 95 are spaced from one another leaving a centralportion 97 in between the two groups of ribs with no ribs. Thisarrangement may provide a greater amount of support within the groups93, 95 than in the central portion 97 while overall the pad 82 remainscompliant.

The tracks 84 are affixed to the support frame 16. More specifically,the tracks 84 are mounted to a forward surface of the upright supportposts 18, between the support frame 16 and the suspension mesh 14. Thetracks 84 each include a series of vertically spaced elongated detents94 in the form of recesses, holes, or dents. The tracks 84 have acontoured shape to match that of the upright support posts 18 and thesupport frame 16.

In the illustrated embodiment, the tracks 84 are affixed to the uprightsupport posts 18 with shoulder screws 95 that extend through oversizedmounting holes 96 through the track 84. As shown, for example, in FIGS.26 and 27, the shoulder screws 95 may be inserted through oversizedmounting holes 96 so as not to impede the flexibility of the backsupport 12 and to enable the track 84 to pivot slightly with respect tothe frame 16. This connection may ensure that the tracks 84 stayparallel to one another as the frame 16 is flexed by the user andprevent binding of the carriage 86 that is mounted between the tracks84. Of course, other means of attaching the tracks 84 to the uprightsupport posts 18 are contemplated, including snaps and other fasteners.

The carriage 86 attaches to the lumbar pad 82 to enable adjustment ofthe pad 82. As shown, the carriage 86 includes a handle 98 and a pair ofopposed lateral portions 100. The handle 98 is generally centeredbetween the upright support posts 18 and is designed to be bothaesthetically pleasing and functional. The handle includes a centralfingertip portion 102 that extends rearward through the window 23 suchthat it is accessible by a user to adjust the position of the lumbar pad82. As such, at least a portion of the lumbar pad 82 is visible (fromthe rear of the office chair 10) within the window 23.

The carriage 86 is configured to be vertically moveable along the spacedtracks 84 to adjust the vertical position of at least a portion of thelumbar pad 82. The lateral portions 100 of the carriage 86 areconfigured to mount the carriage 86 to the tracks 84. The lateralportions 100 are substantially mirror-image of one another and each hasan upper arm 104 and a lower arm 106. In one embodiment, the upper 104and lower 106 arms are spaced a sufficient distance from one another todistribute the torque from the handle 98 as the handle 98 is adjusted bya user. A spring mechanism is mounted to and between the upper and lowerarms 104, 106 and includes a detent spring 108 having two v-shaped legs110 and a center tab 112. The center tab 112 is mounted to a post 114integral to the lateral portion 110 and is affixed using a rivet, screw,or other suitable fastener. The center tab 112 also includes an offsetnub 116 positioned to interface with the detent 94 of the track 84. Thelateral portions 100 and detent spring 108 are spring loaded against thedetents 94 with enough bias that the vertical position of the lumbar pad82 can be retained at a desired position.

An irregularly shaped spring wire 118 slidably retains the carriage 86,and more specifically the lateral portions 100, to the tracks 84. Thespring wire 118 includes spaced horizontal bars 122 and a vertical bar124 extending therebetween. The upper and lower arms 104, 106 of thelateral portion 100 each include a retention tab 120 and the horizontalbars 122 are positioned under and retained by respective retention tabs120. The vertical bar 124 is positioned under and retained by the post114 formed in the lateral portion 100. The horizontal bars 122 looparound the distal edge of the track 84, helping to retain the lateralportion 100 (and thus the carriage 86) against the track 84. As, thespring wire 118 is held in position, the lateral portion 100 is able toslide laterally along the spring wire 118. That is to say, the retentiontabs 120 and post 114 retain the lateral portion 100 between the springwire 118 and the track 84 in the fore-aft direction, yet allow movementof the lateral portion 100 and carriage 86 in the side-to-sidedirection. As the carriage moves in the side-to-side direction, thev-shaped legs 110 on the spring mechanism 108 act on the spring wire 118to bias the carriage 86 in a generally centered position.

The lumbar pad 82 is mounted to the carriage 86 with spaced fasteners orretention clips 130. These retention clips 130 extend through the upperarms 104 of the lateral portions 100 of the carriage 86. In theillustrated example, the retention clips are shown as “Christmas tree”type fasteners, though other fasteners may be suitable. The rear of thelumbar pad 82 includes two through holes (not shown) into which theretention clips 130 are inserted. In one embodiment, the lumbar pad 82includes structure for fixing the lumbar pad 82 in place with respect tothe suspension mesh 14. As shown, the front of the lumbar pad 82includes a center tongue 134 that extends outwardly from the surface ofthe lumbar pad 82. The center tongue 134 is adapted to be receivedwithin an opening formed by the horizontal and vertical support members40, 42 of the suspension mesh 14. More particularly, in the illustratedembodiment, the center tongue 134 is a rectangular protrusion extendingfrom the surface of the lumbar pad 82, and the shape and size of therectangle matches the shape and size of one of the rectangular openingsin the suspension mesh 14 that is formed between adjacent horizontal 40and vertical 42 support members. Together, the center tongue 134 andretention clips 130 mounted to the carriage 86 provide a “rolling”motion of the lumbar pad 82 when the vertical position of the carriage86 is adjusted by a user manipulating the handle 98.

As described above, the two lateral portions 100 are substantiallymirror-images of one another, and each lateral portion 100 is slidablymounted to the respective track 84, which is independently mounted tothe support post 18. The v-shaped spring legs 110 of the detent spring108 are positioned to contact the vertical bar 124 of the spring wire118. In the case that the carriage 86 is shifted to the left (toward thecenter of the chair), in the view shown in FIG. 24, the detent spring108 is also pulled to the left, forcing the legs 110 to spread apart orflatten and applying a force to bias the carriage 86 back to the right.In the opposite case, illustrated in FIG. 25, where the carriage 86 isshifted to the right (away from the center of the chair), the detentspring 108 is also moved to the right, allowing the legs 110 to relaxand move closer together, reducing the applied force.

The lateral portions 100 work together such that when the carriage 86 isshifted in one direction, one detent spring 108 applies a force in theopposite direction, and the opposite detent spring 108 relaxes. Thisrelationship enables the carriage 86, and more specifically the handle98, to stay centered within the window 23 of the back support 12.Additionally, the detents 94 in the track 84 are elongated in thelateral direction, and as the detent spring 108 moves side-to-side, thenub 116 is able to move side-to-side within the detent 94 without losingretention.

The design of the lumbar support unit 80, and in particular the designof the spring wire 118 and v-shaped legs 110, keeps the handle 98centered within the window 23 of the back support 12 while enabling adegree of lateral movement of the carriage 86 through a range oftolerances, angles, and locations. As a result, the lumbar mechanism 80can “float” side to side to allow tolerance and production variabilityof the back support 12, and as the back support 12 and frame are twistedfrom side-to-side under the force of an occupant's back. As describedabove, the support posts 18 have a controlled degree of torsionaldeflection and resiliency, and the float provided to the lumbarmechanism 80, along with the degree of pivoting flexibility between thetracks 84 and the support posts 18, can prevent racking or bindingbetween the carriage 86 and the tracks 84 when the back support 12 istorsionally deflected.

Additionally, the design and placement of the handle 98 providessubstantially torque resistant movement of the carriage 86 along thetracks 84. More particularly, the handle 98 is vertically spaced fromthe point at which the carriage 86 is mounted to the tracks 84, as wellas the point at which the lumbar pad 82 is mounted to the carriage 86.This vertical space can prevent torsional binding between the carriage86 and the tracks 84 when the lumbar mechanism 80 is raised or loweredby the user. In the illustrated example, the handle 98 is positioned atthe vertical midpoint between the upper 104 and lower 106 arms of thecarriage 86 to reduce torque on the handle as noted above; however, itshould be understood that the handle 98 could also be positioned at adifferent mounting point of the carriage 86.

Referring to FIGS. 28-36 three positions of the lumbar mechanism 80 areillustrated with the lumbar pad 84 in position between the suspensionmesh 14 and the frame 16. Notably, the lumbar pad 84 is generallycylindrical prior to insertion between the suspension mesh 14 and theframe 16, but the flexible nature of the pad enables the pad 84 todeform when compressed between the suspension mesh 14 and the frame 16.The position shown in FIGS. 29, 32, and 35 defines a mid or homeposition. In the home position, the lumbar pad 82 is generally ovate andis positioned at a mid-level height along the tracks 84. To move thelumbar mechanism 80, a user grasps the handle 98 and moves it up ordown, forcing the nubs 116 to incrementally skip to adjacent detents 94.As noted above, the lumbar pad 82 rolls with respect to the suspensionmesh 14 when the vertical position of the lumbar mechanism 80 isadjusted by a user. The rear of the lumbar pad 82 is affixed to thecarriage 86 and moves up or down with the carriage 86 and a portion ofthe front of the lumbar pad 82 stays in the position with respect to thesuspension mesh 14 because the tongue 134 is retained by the suspensionmesh 14, resulting in the rolling motion—similar to the motion of a tanktread, albeit with the tongue 134 fixed on the suspension mesh 14—of thelumbar pad 82.

More specifically, in a first position of the lumbar pad 84, a firstportion 140 of the lumbar pad 82 engages and is compressed against afirst portion 150 of the rear surface of the suspension mesh 14. Movingthe handle 98 of the lumbar mechanism 80 causes the lumbar pad to rollsuch that an adjacent second portion 142 of the lumbar pad 82 rolls intocontact with an adjacent second portion 152 of the rear surface of thesuspension mesh 14. This provides continuous rolling engagement of atleast a portion of the lumbar pad 82 on the rear surface of the mesh 14.

The lumbar position illustrated in FIGS. 28, 31, and 34, defines alowered position. The user pulls the handle 98 downward, forcing thenubs 116 to skip down to one of the lower detents 94. The rear of thelumbar pad 82 is pulled down, while the tongue 134 portion of the lumbarpad 82 remains in place. This rolls the lumbar pad 82 down in the mannerof a tank tread, providing lumbar support to a lower region of the backsupport 12. In this lowered position, the first portion 140 and thesecond portion 142 engage the first and second portions 150, 152 of thesuspension mesh 14.

The lumbar position illustrated in FIGS. 30, 33, and 36, defines araised position. The user pulls the handle 98 upward, forcing the nubs116 to skip up to one of the higher detents 94. The rear of the lumbarpad 82 is pulled up, while the tongue 134 portion of the lumbar pad 82remains in place. This rolls the lumbar pad 82 upward, providing lumbarsupport to a higher region of the back support 12. In this raisedposition, the first portion 140 and a third portion 144 engage the firstportion 150 and a third portion 154 of the suspension mesh 14.

It should be understood that intermediate lumbar mechanism 80 positionsare possible as the lumbar pad 84 is rolled up and down the rear surfaceof the mesh 14, and are not limited to the three illustrated. In analternative embodiment, the lumbar mechanism 80 may be used inconnection with any flexible back support surface to provide continuousadjustable support along any desired region of the back support surface.The lumbar mechanism 80 may be positioned with the nubs 116 seated inany of the detents 94. In another embodiment, the lumbar mechanism 80may roll without the use of specific detents.

III. Manufacture

The above back support 12 is presented in greater detail in connectionwith the flow chart of FIG. 16. In particular, the flow chart of FIG. 16includes a method 200 of manufacturing the back support. The method 200including: (a) molding the back support frame; (b) molding thesuspension mesh; (c) mounting the lumbar support to the back supportframe; and (d) mounting the back support frame to the suspension mesh.

Molding the back support frame is depicted as step 202 in FIG. 16. Asdescribed above, the support frame 16 includes the upright support posts18, flexible support arms 20 that extend from the support posts 18, anda spline channel 28 that extends the length of the support posts 18. Thesupport arms 20 are molded in a first curved position A where thesupport arms 20 curve slightly rearward, toward the rear of the chair10.

Molding the suspension mesh back support is depicted as step 204. Thesuspension mesh 14 includes the integral retaining channel 48, radialarrays 46, and the horizontal and vertical tensioning support members40, 42 that together form a flexible mesh.

Mounting the lumbar mechanism 80 to the support frame 16 is depicted asstep 206 and generally includes affixing the tracks 84 to the supportposts 18, affixing the lumbar pad 82 to the carriage 86, and mountingthe carriage 86 between the tracks 84.

Mounting the support frame 16 to the suspension mesh 14 is depicted asstep 208. Mounting the support frame 16 to the suspension mesh 14includes generally aligning the components, flexing the support arms 20forward, and inserting the peripheral edge 24 of each support arm 20into the retaining channel 48 of the suspension mesh 14. Duringinstallation, the supports arms 20 are flexed from the first position A,shown in FIG. 14, into a second position B, shown in FIG. 15. Thedifference between first and second positions A and B is illustrated inFIG. 13. This second curved position B provides a state of tensionbetween the support frame 16 and suspension mesh 14. In this fashion,the support frame 16 and suspension mesh 14 are readily assembled in asubstantially fastener-less, self-retaining process. Further, theinternal assembly force created by flexing the support arms 20 holds thesupport frame 16 and suspension mesh 14 interface secure. In addition,the support arms 20 can be removed from the retaining channel 48 withoutdamaging the components, if needed or desired.

The method 200 continues with providing an upholstery cover, depicted asstep 210. As described above, the upholstery cover 60 has a centralopening 66 and an edging 68 knitted in the perimeter of the centralopening 66. Step 210 also includes inserting an extrusion 70 into theedging 68.

Depicted as step 212, the method 200 continues with positioning theupholstery cover 60 over the assembled support frame 16 and suspensionmesh 14. As described above, the upholstery cover 60 is a substantiallycontoured pocket with an open lower end 64. The upper edge of theassembled support frame 16 and suspension mesh 14 is inserted into theopen lower end 64 of the upholstery cover 60, which is then pulled downinto place. Once the upholstery cover 60 is in place, the edging 68,with the extrusion 70 disposed therein, is pressed/inserted into thespline channel 28 in the upright support posts 18 of the support frame16, as depicted in step 112. This configuration attaches the upholsterycover 60 to the support frame 16, enabling the upholstery cover 60 to bemounted to the back support 12 without additional fasteners or adhesive.

Lastly, the assembled back support 12 may be affixed to a chair frame tocomplete the office chair 10, depicted as step 214. A fastener, such asa conventional screw, is installed, from a lower surface, through thebase 5 and into the wedge base 22, connecting the components primarilyin tension.

The back support 12 described herein provides a compliant backrest thatflexes to accommodate a large range of motion and postures of the seatedoccupant. Further, the individualized nature of the support arms 20allows for localized flexing to accommodate postural movements of theoccupant, for example reaching or changes in seated posture. When anoccupant sits in the chair 10, the flexible support arms 20 andsuspension mesh 14 comply with the back of the individual, increasingthe contact area between the back support 14 and the occupant's back,while continuing to bias them towards the desired ergonomic contourprovided by the suspension mesh.

In summary, the support characteristics of the back support 12 may betuned to a desired profile by varying the features of the back supportframe. Support characteristics of the suspension mesh 14, support frame16, and lumbar mechanism 80 are each individually modifiable, and themodifications to the individual components in combination with oneanother effects the overall support characteristic of the back support12. Modifying a characteristic on one component may affect thecharacteristics of another component and/or the back support itself. Forexample, increasing the initial curvature of the support arms 20, whichrequires more flexing of the support arms 20 to attach and retain thesuspension mesh 14, and creates greater tension in the support frame 16.

Combinations of modifications to the individual components results inhighly customizable support characteristics available to design into theoffice chair. Possible combinations of modifications include: (1) numberand spacing of the support arms 20; (2) length and thickness of thesupport arms 20; (3) initial curvature of the support arms 20; (4)width, thickness and spacing of the horizontal and vertical tensioningsupport members 40, 42 of the suspension mesh 14; (5) width, thicknessand spacing of the radial arrays 46 of the suspension mesh 14; (6)degree of stretch of the upholstery fabric 60; (7) positioning of thelumbar mechanism 80; (8) flexibility of the material used in the lumbarpad 82; and (9) spacing and number of annual support ribs 92 of thelumbar pad 82.

The components of the back support 12 of the present invention arereadily assembled in a substantially fastener-less manufacturingprocess. The support frame 16 is mounted to the suspension mesh 14without requiring any type of additional fastener, such as traditionallyused screws or clips. In addition, the support frame 16 can be removedfrom the suspension mesh 14 without damaging either component. This isadvantageous in the case that one of the support frame 16 or suspensionmesh 14 is damaged or defective; the component can be removed, reworked,or reassembled, without having to scrap the viable remaining component.The upholstery cover 60 is also readily assembled in a substantiallyfastenerless process. With the cover 60 in place, the edging 68 andextrusion 70 are pressed into the spline channel 28 on the support frame16. Again, the cover 60 can be removed therefrom without damaging eithercomponent. Accordingly, the back support 12 is readily assembled withoutthe required use of tools.

The above description is that of current embodiments of the invention.Various alterations and changes can be made without departing from thespirit and broader aspects of the invention as defined in the appendedclaims, which are to be interpreted in accordance with the principles ofpatent law including the doctrine of equivalents. This disclosure ispresented for illustrative purposes and should not be interpreted as anexhaustive description of all embodiments of the invention or to limitthe scope of the claims to the specific elements illustrated ordescribed in connection with these embodiments. For example, and withoutlimitation, any individual element(s) of the described invention may bereplaced by alternative elements that provide substantially similarfunctionality or otherwise provide adequate operation. This includes,for example, presently known alternative elements, such as those thatmight be currently known to one skilled in the art, and alternativeelements that may be developed in the future, such as those that oneskilled in the art might, upon development, recognize as an alternative.Further, the disclosed embodiments include a plurality of features thatare described in concert and that might cooperatively provide acollection of benefits. The present invention is not limited to onlythose embodiments that include all of these features or that provide allof the stated benefits, except to the extent otherwise expressly setforth in the issued claims. Features of various embodiments may be usedin combination with features from other embodiments. Directional terms,such as “vertical,” “horizontal,” “top,” “bottom,” “front,” “rear,”“upper,” “lower,” “inner,” “inwardly,” “outer,” “outwardly,” “forward,”and “rearward” are used to assist in describing the invention based onthe orientation of the embodiments shown in the illustrations. The useof directional terms should not be interpreted to limit the invention toany specific orientation(s). Any reference to claim elements in thesingular, for example, using the articles “a,” “an,” “the” or “said,” isnot to be construed as limiting the element to the singular.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A back support for achair comprising: a back frame having a pair of spaced apart supportposts defining a window therebetween, the back frame having a front sideand a rear side opposite the front side; a flexible back support surfacesupported on the back frame, the flexible back support surface extendingover the front side of the back frame, the flexible back support surfacehaving a rear surface facing the front side of the spaced apart supportposts and defining a space therebetween; and a lumbar mechanismincluding a resilient, tubular lumbar pad having an exterior, outwardlyfacing surface, the exterior surface of the lumbar pad positioned in thespace between the support posts and the rear surface of the flexibleback support surface, at least a portion of the lumbar pad engaging theflexible back support surface, the lumbar pad being visible through thewindow in the back frame.
 2. The back support of claim 1 wherein thelumbar pad is compressed between the back frame and the flexible supportsurface.
 3. The back support of claim 1 wherein the lumbar mechanismincludes a handle attached to the lumbar pad, the handle protrudingthrough the window.
 4. The back support of claim 3 wherein the flexibleback support surface is suspended in tension on the back frame.
 5. Theback support of claim 4 wherein the back frame includes a plurality ofspaced apart, flexible support arms extending outwardly from the supportposts, the support arms having ends that define a periphery of the backframe, the flexible back support surface supported on the periphery ofthe back frame.
 6. The back support of claim 5 wherein the flexible backsupport surface is a one-piece, molded suspension mesh.
 7. The backsupport of claim 6 wherein the suspension mesh includes a series ofspaced apart vertical members and a series of spaced apart horizontalmembers that intersect the vertical members.
 8. A back support for achair comprising: a back frame defining thoracic, shoulder, lumbar, andpelvic regions, the back frame having a pair of spaced apart uprightsupport posts, the support posts having upper and lower ends, the upperends joined by an upper support cross member and the lower ends joinedby a lower support cross member, the support posts and cross memberscollectively defining a window in the back frame, the back frame havinga front side and a rear side opposite the front side; a flexible backsupport surface supported on the back frame, the flexible back supportsurface supported in front of the front side of the back frame anddefining a space between the flexible back support surface and the frontside of the support arms; and a lumbar mechanism having a lumbar padwith an outer circumferential surface, the outer circumferential surfacepositioned within the space between the flexible back support surfaceand the front side of the back frame and compressed between the backframe and the flexible back support surface.
 9. The back support ofclaim 8 including at least a portion of the outer circumferentialsurface of the lumbar pad engaging the flexible back support surface, atleast a portion of the outer circumferential surface of the lumbar padfacing the back frame, and a portion of the lumbar pad being visiblethrough the window in the back frame.
 10. The back support of claim 9wherein the lumbar pad is a flexible cylinder having an exteriorsurface, a first portion of the exterior surface engaging the flexibleback support surface and a second portion of the exterior surfaceengaging the back frame.
 11. The back support of claim 8 wherein theflexible back support surface is suspended in tension on the back frame.12. The back support of claim 8 wherein the back frame includes aplurality of spaced apart, flexible support arms extending outwardlyfrom the support posts, the support arms having ends that define aperiphery of the back frame, the flexible back support surface supportedon the periphery of the back frame.
 13. The back support of claim 8wherein the flexible back support surface is a one-piece, moldedsuspension mesh.
 14. The back support of claim 13 wherein the suspensionmesh includes a series of spaced apart vertical members and a series ofspaced apart horizontal members that intersect the vertical members. 15.The back support of claim 8 wherein the flexible back support surface isvisible through the window.
 16. The back support of claim 8 wherein thewindow extends through at least two of the thoracic, shoulder, lumbar,and pelvic regions.
 17. The back support of claim 16 wherein the windowextends through the thoracic, lumbar and pelvic regions.
 18. The backsupport of claim 17 wherein the cross members are shorter than thesupport posts, such that the window has the shape of an elongatedrectangle.
 19. The back support of claim 18 including an upholsterycover extending over the flexible back support surface and a portion ofthe back frame, the upholstery cover defining a central opening alignedwith the window.
 20. The back support of claim 8 wherein the flexibleback support surface includes a flexible periphery that defines aretaining channel, the back frame defining a peripheral edge extendinginto the retaining channel to retain the flexible back support surfacein suspension on the back support frame.
 21. The back support of claim 8wherein the support characteristics provided by the combined back frameand flexible back support surface are different in the differentregions.
 22. The back support of claim 8 wherein the support posts eachhave a vertical length defining an axis, and where each of said uprightsupport posts twists independently from the other about its axis uponreceiving a force from a user on the flexible back support surface.